This invention relates to polyoxyalkylene polyamines having secondary amino groups at their terminals.
Polyoxyalkylene polyamines find use as a polyamine component of polyurea elastomers, polyurea reaction injection molding (RIM) and other polyurea products. One of disadvantages of polyoxyalkylene polyamines is the increased reaction rate with polyisocyanates. Thus, they tend to cause premature curing when used in polyurea RIM. This is particularly true when the polyoxyalkylene polyamine is trifunctional because the resulting polyurea polymer assumes a three dimentional network structure.
It has been known that the reaction rate of a primary polyoxyalkylen polyamine with a polyisocyanate may be decreased by modifying the primary amine to the corresponding secondary amine. See, R. A. Grigsby, Jr. and D. M. Rice, "Modified Polyetheramines in RIM", J. Elastomers and Plastics, 23, 54-65 (1991). One of such modification methods comprises the cyanoethylation of primary amino groups with acrylonitrile which is known to be highly toxic, explosive and flammable.
U.S. Pat. No. 4,431,790 corresponding to EP-A-0046088 discloses a secondary polyoxyalkylene polyamine produced by reacting the corresponding primary amine with a hydroxyalkyl acrylate or methacrylate.
This patent also discloses that the reaction product has a significantly decreased reactivity with a polyisocyanate compared to the starting primary amine and thus is useful as a curing agent in the manufacture of polyurethane polymers from polyols and polyisocyanates. It has been discovered, however, that polyoxyalkylene polyamines modified with a hydroxyalkyl acrylate or methacrylate still tend to cause premature curing in the absence of a polyol.
U.S. Pat. No. 5,075,503 issued Dec. 24, 1991 disclosese hydrazine terminated polyoxyalkylene polyamines useful as latent epoxy curing agents or chain extenders for polyurea polymers. The hydrazine terminated polyetherpolyamines are synthesized by the two step reaction of reacting a polyoxyalkylene diamine with an alkyl acrylate followed by the aminolysis of the resulting adduct with hydrazine. This patent, however, does not address to the secondarization of trifunctional polyoxyalkylene polyamines which are more acute than the secondarization of the corresponding diamines in the polyurea RIM.
Accordingly, a need exists for a trifunctional secondary polyoxyalkylene polyamines having a moderate reactivity in the polyurea RIM.